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So this has now been made good with new connectors. The only things I found wrong was the braided sheath on the knock sensor connection had perished. The idle and wide throttle micro switches also seem to be ok for switching function and set. I've got a hold of the original VW fault diagnosis document for Digifant (from the guy who set timing / mixture for me) and checked that all of the resistances in each of the components are within spec, which they are. I've belled out all of the cables from the sensors and switches back to the ECU connector and have continuity to each. I matched part numbers from the old to new, but that doesn't guarantee that the old were correct for the car I suppose! I'm now starting to question if some of the new parts may be incorrect (coiul or injectors maybe). I was really optimistic that this would sort the car, but it's exactly the same! They did however find the Airflow meter out of spec at the lower rev range, so they have just repaired this (excellent service from ATP if a tad pricey!). I've just had the Engine ECU evaluated for error states by ATP who concur that their previous repair of the ECU some 21 years prior leaves the ECU functioning correctly. But struggling to believe that makes any difference. One thing that I'm not 100% sure is correct is what parts of the throttle body vac ports go to what, but have plumbed to what diagrams I can find on the web. I've been all over it with the carb cleaner spray and can find no evidence of a vac leak (even plugged the feed to the clocks to ensure its now an MFA vac feed leak).
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GUNSON GASTESTER MK2 FULL
Throtttle body is like new after full strip and rebuild.Bosch super 4 plugs (I've elected for these having used them in newer cars and been happy with them.I don't have a CO meter / strobe, so have watched my local garage (who I know used to work lots on Mk2's back in the day as I used to buy parts from them sometimes) set this to Jonny's spec, and likewise with the timing strobe. A key off, key on again resolved this and it'll fire into life. Very occasionally it'll struggle to fire when hot.On occasion there will also be a moment's hesitation as you accelerate through 3800 rpm under hard load (not sure if this is related or a totally separate issue).Occasionally will surge up to about 1200 rpm that will correct most of the time with a blip of the throttle.I've utlised Jonny's excellent Digifant tune up guide (thanks Jonny), and trawled lots of forums for inspiration of other things to check, but whatever I do leaves it with a really poor tickover. I've extensively rebuilt it so the majority of the parts are new. I just cannot nail it, and it's really getting to me now. I'm really hoping that someone can shed some light on a poor idle issue that I've been struggling to resolve for many months now.